Injectors for accumulator injection systems are known in various embodiments. A known injector of this type is illustrated by way of example in FIG. 4. Here, fuel is delivered into the surrounding region of the nozzle needle 36 via a high-pressure feed line 30. The nozzle needle 36 is in contact with a control piston 31 which is arranged with one end in a control space 32. The pressure in the control space 32 can be controlled in a known way via a control valve 33, so that the control space 32 can be connected to a tank T. That side of the control piston 31 which is opposite the control space 32 is in contact with a low-pressure space 34 which is connected to the tank T via a low-pressure outflow 35. As a result, the nozzle needle 36 can lift off from its seat in a known way and injection can take place.
In the injector concept shown in FIG. 4, however, a permanent leakage occurs in the nozzle needle guide 37 and in the guide 38 of the control piston 31, since the spaces acted upon by high pressure are connected to the low-pressure space 34 via sealing gaps. A fuel quantity therefore flows from the high-pressure region to the low-pressure space 34 via the two guides 37 and 38. However, this permanent leakage causes an appreciable loss of efficiency.